Osteoarthritis (OA) affects 27 million Americans, many of whom have concomitant symptomatic meniscal tear. Arthroscopic partial meniscectomy (APM) is the surgical procedure used to treat these patients when conservative measures are not successful. The efficacy of APM in patients with OA has not been studied rigorously. Prior studies have raised the concern that APM may be associated with accelerated progression of OA, however these studies have not used appropriate controls. Thus the clinical community faces uncertainty both about the short term efficacy of APM and its longer term effects in patients with symptomatic meniscal tear and OA. Currently funded aims: The MeTeOR Trial was funded to 1) establish whether APM provides greater pain relief and functional improvement over six months as compared with nonoperative therapy;2) follow subjects for two years to ascertain whether short-term are sustained;and 3) examine the cost- effectiveness of APM for patients with symptomatic meniscal tear and knee OA. Aims of the Competitive Revision: The proposed revision addresses the crucial question of whether APM accelerates structural progression of OA compared to non-surgical management. It also examines the clinical meaning of progression in structural parameters. These objectives lead to four Specific Aims: 1.To obtain radiographs and MRI studies as well as questionnaire data from subjects at 18 months from study enrollment. 2.To conduct standardized readings of the radiographs and MRI scans using Kellgren-Lawrence grading for radiographs and the semi-quantitative Boston Leeds Osteoarthritis Knee Score (BLOKS) scoring system and quantitative 3-D cartilage morphometry for MRI. 3.To develop an integrated MeTeOR database that couples clinical data with a centralized repository of longitudinal (baseline and 18 month) radiographs and MRI studies in order to prepare for analyses of differences in rates of OA progression between the two trial arms. 4.To establish the inter- and intra-rater reliability of imaging findings and clinical interpretation of changes in imaging parameters. The study activities will build the evidence to inform clinicians and policy makers of short-term benefits and longer term effects of APM and nonoperative management of meniscal tears in patients with OA.